A non aqueous electrolyte secondary battery having high electromotive force in which there is a non aqueous electrolyte and lithium ions transfer between a positive electrode and a negative electrode has recently been utilized as a new type high output and high energy secondary battery.
In such a non aqueous electrolyte secondary battery, a lithium transition metal composite oxide such as LiCoO2 has been used as the positive electrode, a carbon material which is capable of occluding and discharging lithium metal, a lithium alloy or lithium has been used as the negative electrode, and an organic solvent, such as ethylene carbonate and diethyl carbonate, which dissolves a solute comprising a lithium salt such as LiBF4 and LiPF6, has been used as the non aqueous electrolyte.
However, in such non aqueous electrolyte secondary battery in which charging and discharging takes place by movement of lithium ions between the positive and negative electrodes, the organic solvent of the non aqueous electrolyte is reduced in capacity by decomposition, and the organic solvent is combustible and there is a risk of the battery burning when the battery is under an unusual condition, for example, excessive charge.